The world for my setting is a divinely-created flat world with a sky dome over it. It floats amidst the roiling elemental chaos and thus needs something to hold it together. That something is a set of five elemental nodes, one for each of the five elements (earth, fire, wood, metal, and water). Water (cold) is in the north, wood in the east, earth in the center, metal in the west, and fire in the south. These nodes influence the weather, terrain, and flora & fauna in their area of the world.
Note the different water depths, which go from shallower in the south to deeper in the north. The northern continent is really just a huge ice mass. Naturally there are miles of tunnels and caves down in there. Also, see the ice island over on the west? I plan to have a huge iceberg perpetually circling it on currents. Carved into it is an ice city inhabited by the descendants of the followers of an exiled dwarf who tried to crown himself emperor. Due to the magical basis of the island having formed around something in the first place, the dwarves there are all now creatures of elemental cold. The cold preserves them in a sort of immortality--as long as they stay on the iceberg.